The bed is quite high above the floor so there is about 0.5 m distance between the bed and the floor and that's where the extra bed is. I didn't hear too much complains about the extra bed but a reading lamp will be added.

I glued 10 mm high density foam on the beams on the trailer frames to avoid compression of the sandwich. I have secured the cabin to the frame of the trailer on several places. I have some cracks in one area where the structure has done some resistance to the movemet of the trailer.

The german guy that was my inspiration was actually talking about a mk II version of his box and he had the same ideas as you, a giant box for both the boat and beds.

/hakan